Crack propagation behavior and toughness of V‐notched polyethylene terephthalate injection moldings

Abstract

The role of the skin and core regions in controlling the effects of V-notches, on the fracture behavior of PET injection-moldings, was correlated with their tensile and impact properties. Investigations revealed that there were three distinct fracture behaviors: ductile, semiductile, and brittle fracture transitions. The notch sensitivity factor for strength (K S ) in the ductile and semiductile transitions indicates that the fracture strength was not sensitive to 1.5 mm deep notches, which is considered the skin region. The introduction of core-deep notches (>1.5 mm) resulted in a rapid increase in K S . On the other hand, the notch sensitivity factor for energy (K T ) shows that the fracture energy was not sensitive at 0.5 mm deep notches. However, K T increased drastically when notches >0.5 mm deep were introduced. The development of an anisotropic skin-core structure in injection moldings is well acknowledged. This is revealed in a constant fracture behavior between 0.6 and 1.0 mm deep notches. Notably, there was a drastic change in the fracture pattern from ductile to semiductile at a critical 0.6 mm deep notch. The specimens experienced a mixed fracture behavior at 1.5 mm deep notch, which marks a transitional fracture pattern at the interface between the skin and core regions. Lastly, a constant fracture behavior was observed at notch depths !1.5 mm. Results show that crack opening, in the samples that had semiductile fracture, was a postnecking phenomenon. Before shear yielding, two shear lines that intersected at 45 were seen to originate from the crack root when a 1.2 kN load was applied. Conversely, crack opening and failure occurred simultaneously in brittle fractures. It is obvious that V-notches provided a gradual transition in fracture behavior from the skin to the core regions, which confirms that the fracture behavior of PET injection moldings can be dependent on the skin and core structure.

Enhanced Impact Strength of Recycled PET/Glass Fiber Composites

“…As can be seen, the presence of the 2 mm deep A-type notch drastically reduces the impact strength. A similar reduction in the presence of a 2 mm-deep notch has been reported by Ogazi-Onyemaechi et al [28], who studied the effects of V-notches on the fracture behavior of injection-molded PET.…”

Thermal decomposition kinetic and flame retardancy of CaCO3 filled recycled polyethylene terephthalate/recycled polypropylene blend

“…Both recycled polyethylene terephthalate (RPET) (viscosity average molecular weight ¼ 23,131 g/mol) 25 and recycled polypropylene (RPP) (MFI ¼ 15 g/10 min) in the form of flake (from crushed waste bottles) were provided by Yasuda Sangyo (Japan). A finely ground commercial grade CaCO 3 (SOFTON 1200) with an average particle size of 1.8 mm was purchased from Bihoku Funka Kogyo (Japan).…”

Structure and Properties of Reactively Extruded Opaque Post-Consumer Recycled PET

“…Figure 4 shows the WAXS patterns of the selected PET samples that were nonisothermally crystallized from the melt by cooling at 20 • C/min. The WAXS patterns of the three samples examined revealed a semicrystalline structure with reflections characteristic of the crystallographic planes (011), ( 010), (110), and ( 100 The virgin PET is used as a reference in this work, and it does not contain Ti ever, r-PET is a post-consumer material that contains PET from different sources nium dioxide particles. Therefore, a direct comparison is not possible in qu terms.…”

“…Figure 3a shows that all samples melt at different temperatures, reflecting t the crystallographic planes (011), ( 010), (110), and (100) for scattering angles at 2θ = 16.59°, 17.81°, 23.04°, and 26.25°, respectively [46]. The unit cell of PET is triclinic with a = 4.56A, b = 5.94A, c = 10.75A, α = 98.5°, β = 118°, and γ = 112° [47].…”